Process and apparatus for the sorting of two or more materials



E. CONDOLIOS Jan. 3, 1967 PROCESS AND APPARATUS FOR THE SORTING OF TWO OR MORE MATERIALS 5 Sheets-Sheet 1 Filed Dec.

.5 mm L m0 V0 3 C E a x 14 TTUR/VEXS Jan. 3, 1967 E. CONDOLIOS 3,295,677

PROCESS AND APPARATUS FOR THE SORTING OF TWO OR MORE MATERIALS Filed D90. 5, 1963 5 Sheets-Sheet 2- INVENTOR. EL /5 Cmvaouos 14 ITO/F/VEX E. CONDOLIOS Jan. 3, 1967 PROCESS AND APPARATUS FOR THE SORTING OF TWO OR MORE MATERIALS Filed Dec. 5, 1963 5 Sheets-Sheet 3 INVENTOR. fZ/E 6'0/v004/0s Jan. 3, 1967 E. CONDOLIOS 3,295,677

PROCESS AND APPARATUS FOR THE SORTING OF TWO OR MORE MATERIALS Filed Dec. 5, 1963 5 Sheets-Sheet, 4

INVENTOR. 62/5 Uwmauas ATIUR/VEX E. CONDOLIOS Jan. 3, 1967 PROCESS AND APPARATUS FOR THE SORTING OF TWO OR MORE MATERIALS 5 Sheets-Sheet 5 Filed Dec. 5, 1963 INVENTOR. flax/0000s BY EL/E United States Patent (3 3,295,677 PROCESS AND APPARATUS FOR THE SORTING OF TWO R MURE MATERIALS Elie Condolios, Grenoble, lsere, France, assignor to Societe Grenobloise dlEtudes et dApplications Hydrauliques, Grenoble, France, a corporation of France Filed Dec. 3, 1963, Ser. No. 327,715 Claims priority, application France, Dec. 7, 1962, 4,514; Oct. 28, 1963, 4,619 20 Claims. (Cl. 209-136) The present invention relates to a sorting process of the type in which use is made of a fluid flow in a duct as the means for sorting particulate materials.

In accordance with the invention a single duct is constructed to subject the particulate materials to two dilferent kinds of fluid sorting, namely (a) one in which the sorting is effected by the entrainment velocity in an inclined duct portion provided with the requisite control means to prevent fine or low-density particles from entering the bottom part of the duct, and

(b) one in which the sorting is effected by the velocity of the material in a second portion of the duct which is vertical and located above the first duct portion; the effect of such sorting by the sinking velocity of the material being to prevent coarse or dense material passing through into the top part of the duct.

A single duct devised to practice the aforesaid steps of the invention is associated with means for causing an upward stream of fluid therethrough, and is provided at the bottom end of the lower inclined duct portion thereof with a restricted cross-section such that the sorting fluid velocity therein is equal to the entrainment velocity of the coarsest or densest particles to be conveyed upwards. The cross-section of the vertical upper duct portion is such that, at a given working concentration, the velocity of the sorting fluid within it is similar to the sinking veloc ity of such coarsest or densest particles. The bulk materials to be sorted are fed in near or in the area in which the inclined and vertical duct portions join, and the sorted materials are recovered at the upstream and downstream ends of the duct.

In the device of this invention, initial coarse separation occurs as soon as the materials are fed into the central portion of the duct either near or within the area in which the said two duct portions join. Most of the fine or low-density particles, with a few coarse or dense particles still among them owing to the imperfection of said initial sorting process, are picked up by .the upward flow and pass into the vertical duct portion. The said vertical portion of the duct has a predetermined cross-section such that for a given rate of flow of the sorting fluid supplied to its bottom end and any additional flow introduced with the material being sorted, the flow velocity in such crosssection will be greater than the sinking velocity of the fine or low-density particles, but less than the sinking velocity of the coarse or dense particles. As a result, the fine or low-density particles will be carried through such vertical duct portion and will be discharged, together with the conveying fluid, at the top of such duct portion, whereas those coarse or dense particles which are picked up by the sorting fluid with the fine or low density particles, and being unable to reach the top of said vertical duct portion, will fall back to the junction area between the two duct portions and slide down the floor of the sloping duct portion.

The remainder of the coarse or dense particles in the material fed into the duct near the junction between such two portions thereof, sink through the top of the inclined duct portion down towards the floor of said portion, carrying fine or low-density particles with them in the process. The coarse or dense particles then slide under gravity down the inclined duct floor against the flow of the sorting fluid and mingle with the coarse or dense particles arriving from the vertical duct portion. The slope of the inclined duct portion is usually between 40 and 60 and is always steeper than the natural equilibrium slope the material would assume in static fluid.

On reaching the lower part of the inclined duct portion, the material enters a zone in which the velocity of the sorting fluid is higher due to the destricted crosssectional area thereof, such velocity being equal, in fact, to the entrainment velocity for the coarsest and densest particles. This increased velocity of the sorting fluid in the said area will slow down the sliding movement of the material and cause a stationary dune of such material to form downstream of the restriction, or in other Words, upwardly in the inclined duct portion from such restriction. The thus formed dune of the material will be continuously stirred and agitated by the current to perfect the washing of the coarse and dense particles, because during the rapid rotary motion of the dune under the influence of such current, any fine or low-density particles that are still entrapped by the coarser and denser particles will be expelled upwards as soon as they pass over the crest of the dune and be carried upwardly by the fluid flow, while the dense or coarse particles will fall into the wake behind the dune and move back towards the latter. As soon as the dune exceeds a certain size, its weight causes it to slide farther down the duct floor to enable a certain quantity of the coarse or dense particles to pass through the restricted section and be discharged from the duct through a suitably positioned device. The extraction of the densest or coarsest particles is thus subjected to an automatically regulated process of separation.

The sorting quanties of a device of the above indicated construction depend largely on the correct observance of adequate proportions between the inclined and vertical duct cross-sectional areas, in relation to the rates of flow of both the sorting fluid and the solid material and the required separation point. The best results are achieved where the entrainment velocity in the restricted lower section, and the velocities in the vertical duct portion, correspond to the same separation point. A remarkable feature of the device is that it is capable of effecting excellent almost optimum separation even should the proportions of the said cross-sectional areas in relation to the fluid and solid material rates of flow not exactly meet the aforesaid conditions, provided, however, that the crosssection of the vertical duct portion be at least slightly larger than the cross-section which would correspond to the separation point for the inclined duct portion. Under these conditions the flow in the vertical duct portion is slower so that particles of intermediate size or density cannot immediately discharge from the top of the duct. As a consequence, the spatial concentration of solid particles in the vertical duct portion will increase, with the result that the velocity of the fluid in it also increases and is thus made to match the entrainment velocity in the inclined duct portion.

A very wide variety of liquids or gases may be employed as storing fluids for the process of this invention. In certain density sorting applications, use might even be made of dense liquids, or of suspensions creating dense media thereby enabling the processing of materials of a wider size range.

In the practice of the invention, the concentration, that is to say, the ratio between the rate of solid material flow at the inlet to the device and the Washing flow, may

reach a high value, such as up to 300 grams/litre in the case of sand in water, and even higher values in certain cases.

It should be noted, that if satisfactory sorting is to be achieved in a closed duct sorting system in which the sorting medium is a fluid, the ratio between the depth of flow and the diameter of the particles to be sorted must be maintained between fairly narrow limits. It therefore follows, that in the use of the device for sorting particles of a given diameter, the depth of the restricted section in the inclined duct portion is fixed between certain limits. If the quantity of material to be processed by one device in a given time is to be increased therefore, this must be achieved by increasing the duct width, as the duct depth cannot be increased.

A device of compact dimensions for practicing the invention may be achieved by forming the duct passages of annular cross-section. In such a device, the lower inclined duct portion will be formed by two cones, and the upper vertical duct portion will be formed by two cylinders, so that the whole device or duct will have a cylindro-conical form. The two cones forming the bottom part or inclined duct portion of the device may have parallel walls, or the wall of one cone may be tapered with respect to the other. Further, the annular space between the two cones may be partitioned in the direction of fluid flow to define passages for the sorting fluid.

In industrial applications, the device will have to take care of variations in the grain size and/or the density of the solid material during the sorting process. In order to enable rapid adaptability of the device to such variations, the invention provides simple means for adjusting the cross-section of the inclined duct portion, such as a means for altering the height setting of the inside cone forming the inner wall of such cross-section in the cylindro-conical form of the device.

With regard to the aforesaid cylindro-conical form of the device, it has been found that there are three preferential arangements in which such form may be employed and which are as follows:

(1) A device working under atmospheric pressure in the usual manner, in which case the dewatering of the sorted materials is accomplished with use of fairly bulky systems, such as screens, which do not yield a very dry product.

(2) A device working under pressure with separate feeds for the sorting fluid and the material. Due to the fact that the equipment is under pressure, this arrangement enables a more satisfactorily internal flow distribution flow distribution to be achieved with excellent drying results. The drying may be accomplished by means of small cyclones with a high operating stability.

(3) A device working under pressure with a common feed for the sorting fluid and material. In this arrangement, which differs from arrangement 2 only as regards its water and material feed, the sorting fluid and the materials to be processed are fed to the device through a common duct, which supplies a cyclone in which the material to be processed is separated from the sorting fluid. The material discharges from the bottom of the cyclone and is then fed into the intermediate part of the device, whereas the washing water discharges from the top of the cyclone and is then fed into the bottom of the sorting duct. The advantages of this arrangement are that it enables the material to be dewatered very efficiently by means of small cyclones with a high operating stability, as in arrangement 2, and that the washing water and solid material are conveyed to the equipment through a single duct and by means of a single pump.

For a better understanding of the invention reference is made to the following description which should be read in connection with the accompanying drawings which show examples of several possible arrangements in which the invention may be practiced, and in which FIG. 1 is a schematic view in longitudinal section of a sorting duct constructed in accordance with the invention;

FIG. 2 is a schematic view showing in central, vertical section a cylindro-conical device constructed to work under atmospheric pressure;

FIG. 3 is a view similar to FIG. 2 showing a cylindroconical device having separate feeds for the sorting fluid and the material and constructed to work under pressure;

FIG. 4 is a view similar to FIGS. 2 and 3 showing a cylindro-conical device in which the sorting fluid and the material are conveyed through a common duct, and constructed to work under pressure;

FIG. 5 is a schematic view showing in central, vertical section a cylindro-conical device provided with stepped surfaces in its lower inclined portion and a double cone in its upper portion; and

FIG. 6 is a diagrammatic composite sectional elevation comparing the construction of a cylindro conical device such as shown in FIG. 2 with the same device provided with faired or streamlined duct contours.

Referring now to FIG. 1 of the drawings, the reference numeral 1 indicates generally the lower inclined portion of a sorting duct constructed in accordance with the invention. Duct portion 1 generally is inclined at an angle of and is tapering in form to provide at its lower end portion an area of restricted cross-section designated 2. Connecting with the upper end of inclined duct portion 2 is a vertical duct portion 3 of constant cross-sectional area throughout its height. The material or mixture to be sorted, consisting of particles of various sizes, is fed in the direction of the arrow 1 into the sorting duct at the juncture of the portions 1 and 3 thereof, through a pipe 4 connected to the sorting duct at the line of such juncture. The mixture is fed to the sorting duct in such a way as to achieve concentrations of up to 300 grams per litre sorting water inflow.

The sorting water is fed in at the bottom of the inclined duct portion 1, as indicated by the arrow 1, and flows up through such inclined duct portion and the vertical duct portion 3. The fine particles of the mixture fed through the pipe 4 and the sorting water discharge through an outlet 9 provided near the open top of the vertical duct portion 3, as indicated by the arrow f2. The coarser particles of such mixture discharge from the bottom end of the inclined duct 1 through a discharge outlet 8, as indicated by the arrow f3.

The restricted cross-section 2 of the inclined duct portion 1 is given a value such that the flow of the sorting water through it is maintained at the entertainment velocity for the coarsest particles to be picked up and conveyed.

The constant cross-sectional area of the vertical duc-t portion 3 is of a value such that the flow of sorting water through such portion is maintained at a velocity which is greater than the sinking velocity of the fine particles of the mixture and lower than the sinking velocity of the coarse particles in such mixture. In order to insure an even distribution of the flow rates in the vertical duct portion 3, an appropriate means, consisting for example of a partition 5 provided with a number of given sized orifices, may be provided in the upper part of such duct portion. The determination of the cross-section of the vertical duct portion 3 will depend on the rate of flow of the water through it, making allowances for any water which might be fed in with the material mixture through the supply pipe 4.

In the use of the sorting duct shown in FIG. 1 of the drawings, the particles fed into the duct through the supply pipe 4 will undergo an initial rough sorting treatment as soon as they are discharged into the duct, with the result that the majority of the fine particles and such coarse particles as may still be among such fine particles, will be carried into the vertical duct portion 3. The fine particles will be conveyed by the washing water up into the upper part of the vertical duct portion 3 and be discharged with such water through the outlet 9, as indicated by the arrow f2. However, the coarser particles carried up into the vertical duct portion 3 cannot rise very far up inside the latter because their sinking velocity is greater than the flow velocity of the water through such duct portion. Consequently the coarser particles will sink back into the junction zone of the duct poitions 1 and 3 and then slide down on the floor 6 of the inclined duct portion 1. As a result of this highly efficient additional sorting action in the vertical duct portion 3, very thoroughly sorted fine particles only containing a negligible proportion of coarse particles are recovered at the top end of such duct portion.

Most of the coarse particles in the material fed in through the supply pipe 4 fall to the floor 6 of the inclined duct portion 1 and in so doing carry some fine particles with them. These coarse and fine particles slide down the duct floor 6 under gravity and joining with the coarse particles coming down from the vertical duct portion 3, proceed downwardly on the floor 6 to the restricted section 2 Where they enter a higher velocity zone in which their sliding motion is stopped and they form a stationary dune 7 under the influence of the flow downstream from or upwardly in inclined duct portion 1 from the restricted section 2. The dune 7 of particles turns over on itself continuously in such way that the fine particles are expelled upwardly as soon as they pass over the crest of the dune, and the heavy particles fall back towards the eddly downstream of the dune. As the particles continue to gravitate down towards the dune and the dune increases in size, its weight also increases and causes it to slide down the duct floor 6, with the result that a certain quantity of coarse material passes through the restrictedzone 2 and discharges from the inclined duct portion 1 through an appropriate outlet 8, as is indicated by the arrow f3. Due to the additional sorting carried on by the dune 7 and which is particularly effective to prevent the fine particles from passing through the restricted zone 2, practicall perfectly sorted coarse particles are recovered through the outlet 8 at the bottom of the sorting duct.

As an alternative to the construction depicted in FIG. 1 of the drawings, the diverging inclined duct portion 1 may be replaced by an inclined duct portion provided With parallel walls and a restricted cross-section in its lower part to form the restricted zone 2.

FIG. 2 of the drawings shows a sorting duct which may generally be considered as being formed by a revolution of the sorting duct shown in FIG. 1 about a vertical axis. This type of construction results in a small compact cylindro-conical device having an annular fluid passage enabling high rates of flow to be obtained. In the construction of FIG. 2, the coaxial cylinders 13 and 13 form the Walls of the vertical, annularly-shaped sorting portion 13 of constant cross-sectional area. An arrangement of given sized nozzles 11 is provided in the upper part of the vertical duct portion 13 both to insure an even flow distribution in such portion and to increase the stability of the sorting device.

The walls of the lower annularly-shaped inclined sorting portion 14- of the device are formed by two coaxial cones 14 and 14" spaced a given distance apart for a given type of mixture to be processed. The spacing of the two cones may be adjusted to enable the device to process various types of materials by altering the height setting of the inner cone 14'. This adjustment may be readily and simply achieved by mounting the cone 14' on a simple screw system known to the art. The restricted section in the inclined sorting portion 14 is formed at 15 by the conical shape of the outside wall or cone 14" and the given conical shape of the inner cone 14'. The cross sectional area of this restricted section or Zone 15 will be proportionately changed with any adjustment of the inner cone 14.

The material to be processed is fed into the device in dry condition at 10 and passes through arrangements which insure its even distribution into the inner cylinder 13 in which the water level is at N The material then sinks down through the water in the inner cylinder 13' and through the annular opening between the latter and the top of the inner cone 14', to reach the transition zone 6 at the juncture between the vertical and inclined duct portions 13 and 14, respectively.

The sorting water is fed to the device by way of a pipe 16 and its rate of flow is kept at a given constant'by suitable devices including an adjustable valve 17 which also controls the flow velocities in both the inclined duct or sorting portion 14 and the vertical duct or sorting portion 13 of the device. The sorting water passes from the pipe 16 down through the inner cone 14 to .a distributing outlet 18 provided at the lower end of such inner cone and having perforations 19 to insure that the inflow of water is evenly distributed within the inclined annular sorting portion 14.

Except that it handles a higher rate of flow, the sorting device of FIG. 2 works in the same manner as the sorting device of FIG. 1, With the fine particles discharging with the sorting water at the level N of the liquid mixture in the vertical duct portion 13, and the coarse particles forming a sorting dune 7 from which particles pass through the restricted section 15 and are discharged through an outlet 20 at the bottom of the sorting duct.

The coarse particles discharging from the device at 20 are conveyed through a pipe 22 to a suitable known dewatering apparatus, such as the screen designated 23, which may discharge the separated particles onto a pile 24-, and the water into a tank 25.

The fine particles and the sorting water spilling from the water level N of duct portion 13 are discharged into an open annular tank 21 at the top of such duct portion, and are conveyed from such tank through a pipe 26 to suitable known dewatering apparatus, such as the screen designated 23 which may discharge the separated particles onto a pile 27, and the water into the tank 25. A pump 28 forces the sorting water collected in the tank 25 through a pipe 29 back to the entry pipe 16 for the recirculation thereof through the sorting device.

The embodiment of FIG. 3 is similar to that of FIG. 2 insofar as the essential method of sorting is concerned, and differs from the latter in the respect that the cylindro-conical sorting device works under above-atmospheric pressure, whereas the embodiment of FIG. 2 works under atmospheric pressure. In the embodiment of FIG. 3, the top ends of the two coaxial cylinders 30 and 31 forming the vertical duct portion of the device are closed oif by two walls 30 and 31, respectively. Both the sorting water and the fine particles rising in the vertical duct portion under pressure are discharged through an outlet 21 in the upper part of such duct portion and into the discharge pipe 26. The coarse particles discharge under pressure from the lower end of the device through an outlet 20 and into a pipe 22 as in the embodiment of FIG. 2.

The material to be processed is delivered at 33 into a tank 35, together with a certain amount of water which is fed into such tank at 34 from a suitable source. The mixture of particles and water is fed from the tank 35 to a pump 36 which feeds such mixture under pressure through a pipe 32 to the upper end of the inner cylinder 31. The water in the mixture serves the two-fold purpose of processing and conveying the fine particles to the vertical duct portion, and as it has a swirling motion, as indicated by the arrow within the inner cylinder 31, it insures that the material to be processed is evenly distributed within the annular intake section 12 at the juncture of the inclined and vertical duct portions.

As in the embodiment of FIG. 2, the sorting water is fed to the equipment at a suitable pressure from a recovery tank 25 by a pump 28 which forces the water through the pipes 29 and 16 and is controlled in its flow to pipe 16 by the flow control valve 17.

The materials discharging from the device through the outlets 20, 21' are conveyed through pipes 22, 26, respectively, to the sorting cyclone separators 37, 37', respectively. As the device is under pressure, the cyclones 37, 37' can be made small and very stable in operation,

thus insuring efiicient dewatering of the sorted materials which may be discharged from the bottom outlets of such cyclones to the heaps 24, 27, respectively. The sorting and conveying water flows separated from the sorted materials discharge from the tops of the cyclones 37, 37 and are conveyed to the recovery tank 25.

In the embodiment of FIG. 4 which like the embodiment of FIG. 3 works under above-atmospheric pressure, both the sorting water and the material to be processed are conveyed to the sorting device in the same pipe. The material to be processed is fed directly to the sorting water recovery tank at 38. The sorting water and the material to be processed are then both drawn by a pump 39 and delivered under pressure by Way of a pipe 40 to a cyclone 41, in which the material to be processed is separated from the sorting water. A valve 42 in the pipe 40 controls the rate of flow of the mixture into the cyclone. The material to be sorted discharges from the bottom of the cyclone at 43 and is fed to the sorting device or duct through the annular section 12 at the juncture of the inclined duct portion and the vertical duct portion of such device. The sorting water discharges from the top of the cyclone 41 through a pipe 44 which conducts such water into the distributor 19 for even distribution into the bottom end of the inclined duct portion. The rate of flow of the washing water through the pipe 44 to the distributor 19 is controlled by a valve 45. It will thus be seen that by this arrangement both the sorting water and the mate rial to be processed are fed to the sorting device through the same pipe 40 and by means of a single pump 39, the mixture thereof on arrival at the device being separated and the material to be processed and sorting water being thus fed to the juncture or transition zone between the vertical and inclined sorting portions, and to the bottom end of the latter, respectively.

The embodiment shown in FIG. of the drawings, is of especial advantage when the sorting fluid is a gaseous material such as air. In the use of air as the sorting fluid, there is a substantial increase in the bulk density of the material being handled than when the sorting is effected with a liquid such as water. Silicium, for instance, the true specific gravity of which is 2.65, has a bulk density ratio of only 1.65 in water, but the bulk density ratio of such material with respect to air is over 1,000. This condition necessitates that when air is employed as the sorting fluid there be a very appreciable increase in the flow velocities in the sorting apparatus, and it has been found that unless special precautions are taken, these higher air flow velocities result in an uneven air flow distribution inside the sorting compartments. It has also been found that unless provision is made when using air as the sorting fluid, there is the likelihood that the layer of particles sliding down the wall of the conical part or inclined duct portion of the apparatus will be sheltered from the air flow, with the result that such layer will slide down so rapidly that air cannot penetrate into it and, consequently, the lighter particles contained in such layer cannot escape. The embodiment of FIG. 5 has been especially designed to minimize the likelihood of the aforesaid disadvantages occurring when air is utilized as the sorting fluid.

In the embodiment of FIG. 5, the sorting apparatus is cylindro-conically shaped as in the embodiment of FIGS. 2 to 4 and comprises an inclined lower sorting section 51 formed by the two coaxial cones 52 and 53, and an upper vertical sorting section 54 formed by two coaxial cylinders 55 and 56. This sorting apparatus operates in a manner similar to that of the embodiments of FIGS. 2 to 4, the mixture to be sorted being fed into the centrally located hopper 57 and sinking down through the inner cylinder 55 to the annular opening 58 through which it is discharged into the juncture zone between the inclined and vertical sorting sections 51 and 54, respectively. The air used in the sorting process is fed into the lower end of the inclined sorting section 51 through a duct 59, the light particles being discharged with the air through a duct 60 at the top of the apparatus, and the heavy particles designated 61 discharging through the bottom duct 59 against the flow of air.

At the top of the apparatus, above the vertical sorting section 54 is a second cone shaped section 50 formed by the coaxial cones 62 and 63 and through which the air and light particles pass on their way to the discharge duct 60. This second cone 50 functions to center the air flow inside the apparatus thereby preventing an uneven air flow distribution inside the sorting compartments 51 and 54. As in the embodiments of FIGS. 2-4, a suitable device, such as the apertured partition 64, is also provided in this construction to insure a more even flow distribution in the vertical sorting portion 54, but such device is constructed to increase the pressure drop across it.

In order to reduce the downward sliding velocity of the particles along the inside surface of the outer cone 53 in the lower inclined sorting portion 51, the slope angles of cones 52 and 53 have been reduced. The inside surface of cone 53 has been provided with annular steps 65, 65 to the same end and additionally to form zones 66, 66 in which the lighter particles are subjected to more intense stirring action so that they escape more readily from such zones 66, 66.

Steps 67, 67 have also been added to the outside wall of the inner cone 52 in order to divert the air flow towards the zones 66, 66 and thereby intensify the stirring action within such zones to provide a more effective separation of the lighter particles.

FIG. 6 of the drawings, as has been described, is a diagrammatic composite figure illustrating to the left of the center line XY the manner in which the air flows in sorting apparatus such as shown in FIGS. 2-5, and illustrating to the right of such center line XY the condition of the air flow in similar sorting apparatus that has been faired or streamline-d especially near the junction zone between the lower inclined duct or sorting portion and the upper vertical duct or sorting portion.

Considering first the left hand side of FIG. 6, it will be noted that in the sorting duct construction shown in the previously described embodiments, the air flow, which 18 indicated by the arrows, as it passes upwardly through the lower inclined duct portion presses hard against the upper portion of the inner cone 72 and breaks away from the upper portion of the outer cone 73 and the lower portion of the outer vertical cylinder 76 as indicated by the zone designated 78. Above the zone 78 the air flow presses hard against the wall of the outer vertical cylinder 76. Because of this action of the air flow there will be set up along the lower end of the inner vertical cylinder 75 a local circulatory or eddy current 77. These conditions of uneven flow distribution at the juncture of the inclined and vertical duct portions and at the lower end of the vertical duct portion substantially affect the sorting qualities of the device. Such disadvantageous condition, however can be overcome by fairing the duct outlines 72, 73' and 75' in the manner shown on the right hand side of FIG. 6, it having been found that by proper design of such duct outlines, any undesirable flow brakeaway and rising currents will be prevented and there will be ensured a more satisfactory air flow distribution inside the vertical sorting compartment.

While I have above described and illustrated in the drawings several forms in which my invention may be embodied, it will be apparent to those skilled in the art that various other forms may be devised with-out departing from the spirit of the invention or the scope of the appended claims.

I claim:

1. A method of achieving very accurate sorting of particulate materials in a fluid flow which comprises causing the fluid flow to enter into the lower end of and to pass up through a lower inclined duct portion and then up through an upper vertical duct portion of certain height joined to the lower duct portion, and feeding the particulate material to be sorted into the fluid flow at an intermediate zone thereof located at the juncture of the two duct portions, causing the velocity of flow of the fluid through the vertical duct portion to be greater than the sinking velocity of the fine or low density particles, but less than the sinking velocity of the coarse or dense particles so that the fine or low density particles are carried by the fluid flow from said intermediate zone to the top of the vertical duct portion and the coarse or dense particles are unable to reach the top of the vertical duct portion, and tend to sink into the lower inclined duct portion and slide down the floor of said inclined duct portion, providing the floor of the inclined duct portion with a slope steeper than the natural equilibrium slope the coarse or dense particles would assume in static fluid, but not of such steepness that the fluid cannot penetrate into a downwardly sliding layer of such particles, and increasing the flow velocity of the sorting fluid at a localized section at the lower end part of the inclined duct portion and downstream of the entrance of the fluid flow into such inclined duct portion so that the velocity of the fluid through such localized section is equal to the entrainment velocity for the coarsest or densest particles in the material and such as to prevent the passage of the fine or low density particles past such localized section.

2. A method such as defined in claim 1 in which the velocity of the fluid through such localized section is such that the fluid flow causes the downwardly sliding particles to form a stationary dune in said inclined duct portion upwardly of such localized section, and continuously stirs and agitates such dune to expel any fine particles that might be entrapped therein, but permits coarse or dune particles to pass through such localized section when the dune exceeds a certain size.

3. A method such as defined in claim 1, in which the fluid is caused to flow in an annularly-shaped stream through said lower inclined duct portion and said upper vertical duct portion, and its feed is controlled at the lower end of said inclined duct portion so that the fluid flow into such inclined duct portion is evenly distributed. 4. A method such as defined in claim 3, in which the discharge of the sorting fluid and the fine or low density particles carried thereby is centered with relation to the annularly-shaped stream passing through said inclined and vertical duct portions.

5. A method such as defined in claim 1, in which the sorting fluid and the particulate material are fed into the sorting duct under above-atmospheric pressure and are maintained under above-atmospheric pressure in the carrying out of the sorting steps.

6. A method such as defined in claim 5, in which the sorting fluid and the particulate material are fed in a common stream to the sorting duct and are then separated to be discharged into the lower end of the inclined duct portion and said intermediate zone, respectively.

7. A method such as defined in claim 1, in which there is created in said inclined duct portion upwardly from said localized section, a localized zone in which the particles sliding down along the floor of said inclined duct portion are subjected to a more intense stirring action than they will meet with at other portions of their path to such localized section.

8. Apparatus for achieving very accurate sorting of particulate materials in a fluid flow, comprising a lower inclined duct portion, a vertical duct portion of given height connected at its lower end to the upper end of said lower duct portion to form a continuous duct, means for feeding sorting fluid into the lower end of said lower inclined duct portion and up through said inclined and vertical portions, and for feeding the particulate material to be sorted into the sorting fluid at an intermediate zone thereof located at the juncture of said inclined and vertical duct portions, means at the upper end of said vertical duct portion for dischanging the sorting fluid flowing up through said inclined and vertical duct portions, said vertical duct portion having a given uniform cross-sectional area such that for a given rate of flow of the sorting fluid fed into said inclined duct portion, the velocity of flow of the fluid through said vertical duct section is greater than the sinking velocity of the fine or low density particles in the material, but less than the sinking velocity of the coarse or dense particles thereof so that the fine or low density particles are carried by such fluid from said intermediate zone to said discharge: means and the coarse or dense particles are unable to reach said discharge means and tend to sink into the lower inclined duct portion, the floor of said inclined duct portion having a slope steeper than the natural equilibrium slope the coarse or dense particles would assume in static fluid, but not of such steepness that the fluid cannot penetrate into a downwardly sliding layer of such particles, and said lower inclined duct portion having a restriction at the lower end part thereof and downstream of the entrance of the fluid flow into such inclined duct portion, said restriction being such that the flow velocity of the sorting fluid is so increased at a localized section in the region of such restriction that the velocity of the fluid therethrough is equal to the entrainment velocity for the coarsest or densest particles in the material, and such as to prevent the passage of the fine or low density particles past such localized section, and a discharge outlet for the coarse or dense particles located below said restriction so that such particles move downwardly in said inclined duct portion past said restriction in their travel toward said discharge outlet.

9. Apparatus for achieving very accurate sorting of particulate materials in a fluid flow, comprising a lower inclined duct portion, a vertical duct portion of given height connected at its lower end to the upper end of said lower duct portion to form a continuous duct, means for feeding sorting fluid into the lower end of said lower inclined duct portion and up through said inclined and vertical duct portions, and for feeding the particulate material to be sorted into the sorting fluid at an intermediate zone thereof located at the juncture of said inclined and vertical duct portions, means at the upper end of said vertical duct portion for discharging the sorting fluid flowing up through said inclined and vertical duct portions, said vertical duct portion having a given uniform cross-sectional area such that for a given rate of flow of the sorting fluid fed into said inclined duct portion, the velocity of flow of the fluid through said vertical duct section is greater than the sinking velocity of the fine or low density particles in the material, but less than the sinking velocity of the coarse or dense particles thereof so that the fine or low density particles are carried by such fluid from said intermediate zone to said discharge means and the coarse or dense particles are unable to reach said discharge means and tend to sink into the lower inclined duct portion, the floor of said inclined duct portion having a slope steeper than the natural equilibrium slope the coarse or dense particles would assume in static fluid, but not of such steepness that the fluid cannot penetrate into a downwardly sliding layer of such particles, and said lower inclinedlduct portion having a restriction at the lower end part thereof and downstream of the entrance of the fluid flow into such inclined duct portion, said restriction being such that the flow velocity of the sorting fluid is so increased at a localized section in the region of such restriction that the velocity of the fluid therethrough is equal to the entrainment velocity for the coarsest or densest particles in the material, and such as to prevent the passage of the fine or low density particles past such localized section, said lower inclined and upper vertical duct portions being annularly shaped, said inclined duct portion being formed by two coaxial cones, and said vertical duct portion being formed by two coaxial cylinders, the lower end of the inner of said coaxial cylinders being spaced from the inner of said coaxial cones to provide an annular discharge opening at the junction of said duct portions, and said feeding means including means for feeding the particulate material into said inner cylinder for entry into said sorting fluid intermediate zone through said annular discharge opening, fluid distributing means provided at the lower end of said inner cone for distributing the fluid evenly into the lower end of said annular inclined duct portion, and means for conveying the sorting fluid to said fluid distributing means.

10. Apparatus such as defined in claim 9, in which said conveying means includes said inner coaxial cone and a pipe extending axially downwardly through the inner of said coaxial cylinders and communicating at its lower end with the interior of said inner cone, the lower end of said inner cone being in communication with said distributing means.

11. Apparatus such as defined in claim 9, in which said feeding means includes a common duct for conveying the sorting fluid and particulate material to the apparatus, and separating means connected to and supplied iby said common duct and associated with said sorting duct so as to discharge the separated particulate material into said inner cylinder, and in which said conveying means is connected to said separating means for receiving the separated sorting fluid for delivery to said fluid distributing means.

12. Apparatus such as defined in claim 9, in which the upper ends of said coaxial cylinders are closed and in which the lower end of the outer of said coaxial cones is closed, said feeding means feeding the sorting fluid and the particulate material into said inclined and vertical duct portions under pressures substantially above atmospheric pressure.

13. Apparatus for achieving very accurate sorting of particulate materials in a fluid flow, comprising a lower in clined duct portion, a vertical duct portion of given height connected at its lower end to the upper end of said lower duct portion to form a continuous duct, means for feeding sorting fluid into the lower end of said lower inclined duct portion and up through said inclined and vertical duct portions, and for feeding the particulate material to be sorted into the sorting fluid at an intermediate zone thereof located at the juncture of said inclined and vertical duct portions, means at the upper end of said vertical duct portion for discharging the sorting fluid flowing up through said inclined and vertical duct portions, means at the upper end of said upper vertical duct portion upstream from said discharge means thereof, for effecting evenly distributed flow rates of the sorting fluid in said vertical duct portion, said vertical duct portion having a given uniform crosssectional area such that for a given rate of flow of the sorting fluid fed into said inclined duct portion, the velocity of flow of the fluid through said vertical duct section is greater than the sinking velocity of the fine or low density particles in the material, but less than the sinking velocity of the coarse or dense particles thereof so that the fine or low density particles are carried by such fluid from said intermediate zone to said discharge means and the coarse or dense particles are unable to reach said discharge means and tend to sink into the lower inclined duct portion, the floor of said inclined duct portion having a slope steeper than the natural equilibrium slope the coarse or sense particles would assume in static fluid, but not of such steepness that the fluid cannot penetrate into a downwardly sliding layer of such particles, and said lower inclined duct portion having a restriction at the lower end part thereof and downstream of the entrance of the fluid flow into such inclined duct portion, said restriction being such that the flow velocity of the sorting fluid is so increased at a localized section in the region of such restriction that the velocity of the fluid therethrough is equal to the entrainment velocity for the coarsest or densest particles in the material, and such as to prevent the passage of the fine or low density particles past such localized section.

14. Apparatus for achieving very accurate sorting of P -W ma erials in a fluid flow, comprising a lower inclined duct portion, a vertical duct portion of given height connected at its lower end to the upper end of said lower duct portion to form a continuous duct, means for feeding sorting fluid into the lower end of said lower inclined duct portion and up through said inclined and vertical duct portions, and for feeding the particulate material to be sorted into the sorting fluid at an intermediate zone thereof located at the juncture of said inclined and vertical duct portions, means at the upper end of said vertical duct portion for discharging the sorting fluid flowing up through said inclined and vertical duct portions, said vertical duct portion having a given uniform cross-sectional area such that for a given rate of flow of the sorting liquid fed into said inclined duct portion, the velocity of flow of the fluid through said vertical duct section is greater than the sinking velocity of the fine or low density particles in the material, but less than the sinking velocity of the coarse or dense particles thereof so that the fine or low density particles are carried 'by such fluid from said intermediate zone to said discharge means and the coarse or dense particles are unable to reach said discharge means and tend to sink into the lower inclined duct portion, the floor of said inclined duct portion having a slope steeper than the natural equilibrium slope the coarse or dense particles would assume in static fluid, but not of such steepness that the fluid cannot penetrate into a downwardly sliding layer of such particles, and said lower inclined duct portion having a restriction at the lower end part thereof and downstream of the entrance of the fluid flow into such inclined duct portion, said restriction being such that the flow velocity of the sorting fluid is so increased at a localized section in the region of such restriction that the velocity of the fluid therethrough is equal to the entrainment velocity for the coarsest or densest particles in the material, and such as to prevent the passage of the fine or low density particles past such localized section, said lower inclined and upper vertical duct portions being .annularly shaped, said inclined duct portion being formed by two coaxial cones, and said vertical duct portion being formed by two coaxial cylinders, the lower end of the inner of said coaxial cylinders ibeing spaced from the inner of said coaxial cones to provide an annular discharge opening at the junction of said duct portions, and said discharge means at the upper end of said vertical duct portion including two coaxial cones provided at the upper ends of the inner and outer cylinders and forming an upper inclined annular duct portion centering the fluid flow discharging from the upper end of said upper vertical duct portion, and a fluid discharge duct connected to the upper end of such upper inclined annular duct portion.

15. Apparatus for achieving very accurate sorting of particulate materials in a fluid flow, comprising a lower inclined duct portion, a vertical duct portion of given height connected at its lower end to the upper end of said lower duct portion to form a continuous duct, means for feeding sorting fluid into the lower end of said lower inclined duct portion and up through said inclined and vertical duct portions, and for feeding the particulate material to be sorted into the sorting fluid at an intermediate zone thereof located at the juncture of said inclined and vertical duct portions, means at the upper end of said vertical duct portion for discharging the sorting fluid flowing up through said inclined and vertical duct portions, said vertical duct portion having a given uniform cross-sectional area such that for a given rate of flow of the sorting fluid fed into said inclined duct portion, the velocity of flow of the fluid through said vertical duct section is greater than the sinking velocity of the fine or low density particles in the material, but less than the sinking velocity of the coarse or dense particles thereof so that the fine or low density particles are carried by such fluid from said intermediate zone to said discharge means and the coarse or dense particles are unable to reach said discharge means and tend to sink into the lower inclined duct portion, the floor of said inclined duct portion having a slope steeper than the natural equilibrium slope the coarse or dense particles would assume in static fluid, but not of such steepness that the fluid cannot penetrate into a downwardly sliding layer of such particles, and said lower inclined duct portion having a restriction at the lower end part thereof and downstream of the entrance of the fluid flow into such inclined duct portion, said restriction being such that the flow velocity of the sorting fluid is so increased at a localized section in the region of such restriction that the velocity of the fluid theretlirough is equal to the entrainment velocity for the coarsest or densest particles in the material, and such as to prevent the passage of the fine or low density particles past such localized section. said lower inclined and upper vertical duct portions being annularly shaped, said inclined duct portion being formed by two coaxial cones, and said vertical duct portion being formed by two coaxial cylinders, the lower end of the inner of said coaxial cylinders being spaced from the inner of said coaxial cones to provide an annular discharge opening at the junction of said duct portions, and means in said lower inclined duct portion for creating therein upwardly from said restriction, a localized zone in which the particles sliding along the floor of said inclined duct portion are subjected to a more intense stinrin'g action than they will meet with at other portions of such floor in the passage of such particles to said restriction.

16. Apparatus such as defined in claim 15, in which said means at said localized zone comprises means projecting from the Wall of the outer cone forming said inclined duct portion into the fluid passageway of said inclined duct portion.

17. Apparatus such as defined in claim 16 in which said projecting means is in the form of an annular step.

18. Apparatus such as defined in claim 15, in which said means at said localized zone comprises means projecting from the wall of the inner cone forming said inclined duct portion into the fluid passageway of said inclined duct portion.

19. Apparatus such as defined in claim 18, in which said projecting means is in the form of an annular shoulder.

20. Apparatus such as defined in claim 15, in which the outer cone of said inclined duct portion and the outer cylinder of said vertical duct portion are shaped to provide a faired outer duct wall portion at the juncture of such duct portions, in which the wall of said inner cone is faired in the region of such juncture of said duct portions, and in which the lower end of said inner cylinder of said vertical duct portion tapers outwardly so as to form with said faired outer duct wall portion, a streamlined duct passageway at such juncture of said inclined and vertical duct portions.

References Cited by the Examiner UNITED STATES PATENTS 1,877,861 9/1932 Hatch 209-l37 X 2,946,439 7/ 1960 Condolios 209-457 3,042,204 7/1962 Eder 209-157 FRANK W. LU'ITER, Primary Examiner. 

8. APPARATUS FOR ACHIEVING VERY ACCURATE SORTING OF PARTICULATE MATERIALS IN A FLUID FLOW, COMPRISING A LOWER INCLINED DUCT PORTION, A VERTICAL DUCT PORTION OF GIVEN HEIGHT CONNECTED AT ITS LOWER END TO THE UPPER END OF SAID LOWER DUCT PORTION TO FORM A CONTINUOUS DUCT, MEANS FOR FEEDING SORTING FLUID INTO THE LOWER END OF SAID LOWER INCLINED DUCT PORTION AND UP THROUGH SAID INCLINED AND VERTICAL PORTIONS, AND FOR FEEDING THE PARTICULATE MATERIAL TO BE SORTED INTO THE SORTING FLUID AT AN INTERMEDIATE ZONE THEREOF LOCATED AT THE JUNCTURE OF SAID INCLINED AND VERTICAL DUCT PORTIONS, MEANS AT THE UPPER END OF SAID VERTICAL DUCT PORTION FOR DISCHARGING THE SORTING FLUID FLOWING UP THROUGH SAID INCLINED AND VERTICAL DUCT PORTIONS, SAID VERTICAL DUCT PORTION HAVING A GIVEN UNIFORM CROSS-SECTIONAL AREA SUCH THAT FOR A GIVEN RATE OF FLOW OF THE SORTING FLUID FED INTO SAID INCLINED DUCT PORTION, THE VELOCITY OF FLOW OF THE FLUID THROUGH SAID VERTICAL DUCT SECTION IS GREATER THAN THE SINKING VELOCITY OF THE FINE OR LOW DENSITY PARTICLES IN THE MATERIAL, BUT LESS THAN THE SINKING VELOCITY OF THE COARSE OR DENSE PARTICLES THEREOF SO THAT THE FINE OR LOW DENSITY PARTICLES ARE CARRIED BY SUCH FLUID FROM SAID INTERMEDIATE ZONE TO SAID DISCHARGE MEANS AND THE COARSE OR DENSE PARTICLES ARE UNABLE TO REACH SAID DISCHARGE MEANS AND TEND TO SINK INTO THE LOWER INCLINED DUCT PORTION, THE FLOOR OF SAID INCLINED DUCT PORTION HAVING A SLOPE STEEPER THAN THE NATURAL EQUILIBRIUM SLOPE THE COARSE OR DENSE PARTICLES WOULD ASSUME IN STATIC FLUID, BUT NOT OF SUCH STEEPNESS THAT THE FLUID CANNOT PENETRATE 